1. Technical Field
The present application relates to lighting source driver circuits, and more particularly to an LED driver having short circuit protection to protect against output short conditions.
2. Description of the Related Art
Light emitting diode (LED) is growing in popularity due to decreasing costs and long life compared to incandescent lighting and fluorescent lighting. LED lighting can also be dimmed without impairing the useful life of the LED light source.
Isolated constant current source topologies that are commonly used in light source (e.g., LED) driver circuits includes flyback converters, forward converters, LLC converters, and half-bridge isolated buck converters. Flyback converters and forward converters have low efficiency and require the use of high-voltage MOSFET devices. LLC converters have insufficient output voltage range, and the output is not self-limiting. Half-bridge isolated buck converters require hard switching of the MOSFET devices, have low efficiency, require complicated controllers, and the output is not self-limiting.
Referring to FIG. 4, an LED driver is shown in prior art. The LED driver provides current having certain duty cycle for the LED. The current is outputted by a controlling module N1 under the control of the switch Q1 which is high frequently turned on or turned off. Because of over-voltage, static, high temperature, and so on, it is ease to damage the switch Q1. When the switch Q1 is out of operation, it will lose the switch function and equal to a wire. As a result, short circuit is occurred, and the output current of the LED driver is directly dropped across the LED so that the LED is burned as it works under of the over-voltage or over-current.
Therefore, it is necessary to provide an LED driver having short circuit protection for settling out the above art problem.